Child abductions have increased markedly in recent years. The search for missing children has made its way to television, on-line services, and various forms of advertising. Demand for deterrents against such abductions have increased.
The most common form of abduction deterrent has been a child alarm. Most child alarms, however, operate as a radio beacon detector. Typically, a child unit sends out carrier pulses on a regular interval which are received by a parent unit. When the parent unit stops receiving the pulses, an alarm condition is established. It is very easy to fool this system: any other pulse on the same carrier frequency will prevent the parent unit from alarming.
Another type of child alarm is similar to the remote activating/deactivating device for car alarm systems. The parent has a transmitter (key fob) that when pressed sends out an encoded radio signal. A loud siren is activated when this signal is detected by the child unit. This type of device is typically classified as a child locator rather than a proximity alarm. Its major drawback is that once the parent and child are out of range of one another, an alarm cannot be triggered.
Moreover, only the child unit alarms. The would-be abductor could physically muffle this alarm, since the parent gets no indication of same.
Other such devices are known, but all suffer from similar drawbacks.
It is therefore an object of the present invention to provide a system which provides an intelligent means of determining child proximity, and in which both a child unit and a parent unit communicate information to one another so that both provide alarm indications at the proper times, and to prevent either unit from being fooled by a decoy.